1. Field of the Invention
The present invention relates to a method of and an apparatus for detecting, analyzing and evaluating characteristics of resin as molding material using an injection molding machine.
2. Description of the Related Art
It is necessary to set a large variety of molding conditions for performing an injection molding operation using an injection molding machine. It takes a long time and requires sufficient experiences to obtaining non-defective product by setting optimum values for the molding conditions. Even if a kind of the resin for use in the injection molding operation is the same, characteristics of the resin have deviation in different lots and defective molding may occur because of the deviation).
It has been developed a pressure curve following control for controlling the injection pressure based on a velocity of the servomotor in learning a gain of the control system so that the injection pressure follows the pressure curve obtained injection producing a non-defective article. In this control, non-uniformity of melting characteristics of the resin in the same lot are absorbed to ensure stability of the molding operation. However, in the case where the temperature of the resin varies greatly, there is a possibility of causing a defective molding by an excessive correction of the injection velocity and therefore it is necessary to set a limit on the correction. It is assumed that this caused by a fact that the control is performed considering only a velocity dependency factor of the resin pressure characteristics which includes the velocity dependency factor and the temperature dependency factor. In order to expand an applicability of this control, it is necessary to clarify the resin pressure characteristics with respect to the velocity dependency factor and the temperature dependency factor and to take the temperature dependence factor into consideration.
As a conventional method of obtaining flux characteristics of the resin, there is known a method of measuring the resin characteristics, such as viscosity of resin, with respect to shearing velocity using a special resin characteristic measuring device.
In the case of determining a difference of the characteristics of resin using an injection molding machines without the special measuring machine, there is known only a method of determining the resin characteristics by comparing the reference pressure curve and the actual pressure curve.
However, in the method of determining a difference in the resin characteristics of different lots by comparing the pressure curves, there is a problem of only a relative difference of resin characteristics in the resin of different lots is obtained and absolute characteristics of resin can not obtained. In the method of measuring the resin characteristics using the special resin characteristics measuring device, since it is difficult to produce the condition same as that in the actual molding operation, i.e., the condition that the molten resin of high temperature and high injection velocity, it is hardly possible to obtain practical results of measurement.